A steam iron may typically be equipped with a vaporization chamber having a heatable bottom surface. During operation, the bottom surface may be heated to a temperature well above the boiling point of water, and liquid water may be brought into contact therewith in order to vaporize it and turn it into steam. The steam may then be discharged to steam outlet openings provided in a soleplate of the iron.
A known problem associated with this procedure, especially at low steam rate settings, is the occurrence of the Leidenfrost effect: a water droplet dripped onto the hot bottom surface of the vaporization chamber may produce an insulating vapor layer that prevents it from rapid vaporization. Instead of instantly boiling, the insulated water droplet may skitter around. At relatively high steam rate settings, on the other hand, which may require actual submersion of the bottom surface, the heating of the water result in a violently boiling and splashing water pool inside of the vaporization chamber. In either case, small water droplets splattering around the vaporization chamber may be entrained in the flow of steam leaving it, and eventually be undesirably spit out of the steam outlet openings.
Several solutions have been offered in the art to eliminate the thus caused spitting behavior of steam irons. One solution employs long and often tortuous steam discharge paths, extending between the steam vaporization chamber and the steam outlet openings in the soleplate, to ensure that small water droplets carried by the steam flow are vaporized before they reach the steam outlet openings. Another solution is described in U.S. Pat. No. 5,390,432 (Boulud et al.). U.S. Pat. No. '432 teaches the combined use of (i) a hydrophilic coating on top of the bottom surface of the vaporization chamber to promote the spreading of water over the surface, and (ii) a screen disposed above the coating, preferably in contact therewith, for fragmenting water droplets dripped thereon. This way, the vaporization performance of the iron is enhanced by forced distribution of water across the bottom surface of the vaporization chamber, and entrainment of skittering water droplets in the outgoing steam flow is prevented. Neither solution, however, appears to work satisfactorily for high steam rates at which the risk of entraining water droplets is greatest. The first solution requires impractically long steam discharge paths to ensure the complete vaporization of all entrained water droplets; the second solution is sensitive to unintended submersion of the bottom surface (due to a necessarily high inflow of water into the vaporization chamber), which may cause the screen to lose its water distributing function.